1. Field of the Invention
The present invention relates to a sheet conveying device, and an image forming apparatus, such as a copying machine or a printer, equipped with the sheet conveying device.
2. Description of the Related Art
Conventionally, in a sheet conveying device for conveying sheets (recording sheets) using roller pairs, if load fluctuation is large when the leading end of a sheet is brought into contact with a roller pair, loss of synchronism of a motor for driving the roller pair can occur, which damages the leading end of the sheet. This phenomenon is likely to occur when a stiff (rigid) sheet is used.
To solve this problem, a technique has already been proposed in which a roller pair is controlled such that the two rollers are separated with a predetermined distance therebetween immediately before a sheet is brought into contact with the rollers, so as to reduce impact between the sheet and the roller pair (see Japanese Laid-Open Patent Publication (Kokai) No. H09-156797).
However, the above-mentioned conventional technique in which contact and separation between the two rollers of the roller pair repeatedly take place is considered to be disadvantageous in that:
(1) The repetition of contact and separation is not suitable for high-speed sheet conveyance;
(2) Sheets can be damaged due to contact and separation between the two rollers;
(3) Since the rollers bound, it takes a certain time period before the rollers are stabilized to provide an appropriate conveying force; and
(4) Load fluctuation is increased when the rollers come into contact with each other.